1. Field of the Invention
The present invention relates to a non-contact driving motor capable of keeping its non-contact state irrespective of its start-up or stoppage condition, thereby obtaining a semi-permanent durability.
2. Description of the Prior Art
Typically, motors, which are used to drive compact precise appliances, have slightly different configurations in accordance with different using purposes, respectively.
In such diverse motors, in particular, motors for a high-speed driving, a hydraulic or pneumatic dynamic pressure bearing is typically used in order to minimize friction generated between a driving member and a fixed member.
When a motor drives at a high speed, the connection portions of a driving member and a fixed member supporting the driving member come into severe contact with each other, thereby generating severe friction. This friction may serve as a load for reducing the driving force of the motor or may generate severe abrasion and noise.
In order to solve such a problem, a fluid such as oil or air is interposed between the connection portions of the driving and fixed members to locally create dynamic pressure between those connection portions. By virtue of such a hydraulic or pneumatic dynamic pressure, the friction generated between the connection portions of the driving and fixed members is reduced, thereby allowing a high-speed driving of the motor.
Referring to FIG. 1, a motor is illustrated which uses a conventional pneumatic dynamic pressure bearing. As shown in FIG. 1, the motor includes a shaft 4 mounted to a circuit board 1 at its lower end, and a sleeve 5 surrounding the shaft 4. A rotor case 6 is integrally formed with the sleeve 5 so that they constitute a rotor assembly rotating about the shaft 4.
The circuit board 1 is provided with a separate holder 2 for firmly holding a stator assembly 3 including a core wound with coils. The rotor case 6 is attached with an annular driving magnet 7 arranged around the stator assembly 3 while being radially spaced apart from the stator assembly 3. The above mentioned configuration is similar to those of typical motors.
In the case illustrated in FIG. 1, the motor also includes a means for supporting axial and radial weights of the rotor assembly during a rotation of the rotor assembly.
That is, upper and lower dynamic pressure generating grooves 4a are formed at the peripheral surface of the shaft 4 inserted in the sleeve 5. The dynamic pressure generating grooves 4a generate dynamic pressure during an operation of the motor, thereby supporting a lateral or radial movement of the rotor assembly, that is, a radial weight of the rotor assembly.
Also, a pair of annular magnets 8 and 9 each of which have opposite poles vertically arranged, are attached to respective facing surfaces of the shaft 4 and rotor case 6 at the upper end of the shaft 4. As shown in FIG. 2, these magnets 8 and 9 face each other in a horizontal direction in such a fashion that the horizontally facing poles thereof have opposite polarities, so that they attract each other at their facing surfaces. By virtue of such an attraction, the magnets 8 and 9 serve to prevent the rotor case 6 from moving vertically with respect to the shaft 4. That is, the magnets 8 and 9 support the axial weight of the rotor case 6.
In accordance with the above mentioned configuration, therefore, the space between the shaft 4 and sleeve 5 in the radial direction of the shaft 4 is maintained by virtue of the dynamic pressure generating grooves 4a, thereby preventing any lateral or radial movement of the rotor assembly whereas the facing magnets 8 and 9 generate an attraction between the shaft 4 and rotor case 6, thereby preventing any axial movement of the rotor case 6.
However, this motor having the above mentioned configuration can be maintained in a non-contact state only when it rotates at a high speed under the condition in which no external impact or load is applied thereto. Under the condition in which the motor is in a stoppage or start-up state, at least the shaft 4 and the sleeve 5 may come into frictional contact with each other in accordance with an external impact or load applied to the motor or the rotating speed of the motor. In the latter case, an abrasion occurs due to the frictional contact, thereby degrading the characteristics of the motor. In particular, such an abrasion reduces the use life of the motor, thereby resulting in a degradation in the product.
Therefore, an object of the invention is to provide a non-contact driving motor which includes a pair of facing magnets having the same polarity at their facing surfaces and serving as an axial and radial weight supporting means, so that it keeps its non-contact state irrespective of its stoppage, start-up, low-speed driving, or high-speed driving condition, thereby achieving an improvement in the driving characteristics thereof.
Another object of the invention is to provide a non-contact driving motor having a complete non-contact drivability, thereby being capable of achieving a great extension of the use lift and an improvement in the reliability of the product.
In accordance with one aspect, the present invention provides a non-contact driving motor comprising: a housing; a sleeve extending upwardly from a central portion of the housing and having a tube shape; stator assembly fitted around the sleeve, the stator assembly including a combination of a core and coils; a vertical shaft rotatably inserted in the sleeve; a rotor assembly including a rotor case centrally coupled to an upper end of the shaft, and an annular driving magnet attached to an outer peripheral end of the rotor case in such a fashion that it faces the stator assembly; an annular first magnet attached to an inner peripheral surface of the sleeve at an upper end of the sleeve; an annular second magnet attached to an outer peripheral surface of the shaft in such a fashion that it faces the first magnet in a horizontal direction; a disc-shaped third magnet fitted around a lower end of the shaft, the third magnet having a diameter larger than the diameter of the shaft; a disc-shaped fourth magnet attached to the inner peripheral surface of the sleeve at a level upwardly spaced apart from the third magnet by a desired distance in such a fashion that it faces the third magnet in a vertical direction; and a disc-shaped fifth magnet attached to a cap covering the lower end of the sleeve at a level downwardly spaced apart from the third magnet by a desired distance in such a fashion that it faces the third magnet in a vertical direction.
In accordance with another aspect, the present invention provides a non-contact driving motor comprising: a housing; a sleeve extending upwardly from a central portion of the housing and having a tube shape; a stator assembly fitted around the sleeve, the stator assembly including a combination of a core and coils; a vertical shaft rotatably inserted in the sleeve; a rotor assembly including a rotor case centrally coupled to an upper end of the shaft, and an annular driving magnet attached to an outer peripheral end of the rotor case in such a fashion that it faces the stator assembly; a disc-shaped first magnet attached to an upper end of the sleeve and magnetized with N and S poles vertically arranged; a disc-shaped second magnet attached to the rotor case in such a fashion that it faces the first magnet in a vertical direction above the first magnet, the second magnet being magnetized with N and S poles vertically arranged in such a fashion that it has the same polarity as the first magnet at facing surfaces thereof; a disc-shaped third magnet attached to an upper surface of a flange integrally formed at a lower end of the shaft, the third magnet being magnetized with N and S poles vertically arranged; a disc-shaped fourth magnet attached to an inner peripheral surface of the sleeve in such a fashion that it faces the third magnet in a vertical direction above the third magnet, the fourth magnet being magnetized with N and S poles vertically arranged in such a fashion that it has the same polarity as the third magnet at facing surfaces thereof; an annular fifth magnet attached to the inner peripheral surface of the sleeve between the first and fourth magnets, the fifth magnet being magnetized with N and S poles radially arranged; and an annular sixth magnet attached to a peripheral surface of the shaft in such a fashion that it faces the fifth magnet in a horizontal direction, the sixth magnet being magnetized with N and S poles radially arranged in such a fashion that it has the same polarity as the fifth magnet at facing surfaces thereof.